The invention relates to a method for controlling the power consumption of a hydrodynamic clutch, in particular as starting element in a drive train by controlling the volumetric efficiency.
During the starting process, i.e. the run-up of the drive motor and simultaneous transmission of torque on the output unit in a drive train, in particular in vehicles but also in stationary units, the problem of energy consumption of the drive motor is increasingly the center of attention since during this process usually too little energy for self-acceleration of the drive motor is available. As starting elements in vehicles hydrodynamic clutches are used for this purpose among other things. They are well-known in a multiplicity of designs. Reference is made to the publication Voith:“Hydrodynamics in motive power engineering”, Vereinigte Fachverlage, Krauskopf Engineer Digest, Mainz 1987. The starting elements are usually integrated in a gear box unit. The gear box unit has for this a first hydrodynamic transmission part and a further second transmission part, which is usually preferably formed by a mechanical transmission part for application in vehicles. Since the power consumption of the hydrodynamic clutch is dependent on its design and not on a machine, which is at least indirectly connected to the hydrodynamic clutch on the output side, during the installation of such a component between a drive motor and a machine it is to be considered that for each load condition between the machine and the hydrodynamic clutch also a state of equilibrium must be ensured between the drive motor and the hydrodynamic component. Thereby the power released by the drive motor is in the rarest case completely available to the gear unit, in particular the hydrodynamic component, during the starting process. Power for auxiliary machines, like for example fans, generators, pumps and so on, which are positioned before the starting element respectively the gear inlet, must thereby be subtracted from the available drive power. For the use of a hydrodynamic component in form of a hydrodynamic clutch the following specified benefits of the hydrodynamic power transmission are thereby desirable for the starting process: wear-free as well as vibration reducing and thermally stable. In connection with drive motors for different application functions concrete demands are made regarding the transfer characteristic also during the starting process. In particular for the application in vehicles a certain behavior during the starting process, in particular a certain power consumption by the impeller of the hydrodynamic clutch, is desired in order to be able to drive the drive motor in an optimized operating range regarding a certain parameter. During the starting process at low speeds it is therefore required that a suitable surplus moment is present for the self-acceleration of the drive motor in order to realize a motor start-up that is relieved as much as possible.